1. Field of the Invention
The disclosures herein generally relate to a treatment agent liquid application device for an ink jet printer. The disclosures, in particular, relate to a treatment agent liquid application device for an ink jet printer that applies a treatment agent such as a blurring inhibitor that inhibits an image blurring in the ink jet printer, which makes ink droplets impact onto an recording medium such as a paper, for example, to form an image, onto a recording surface prior to the image formation.
2. Description of the Related Art
Recently, ink jet printers have rapidly become widespread, since an image formation by an ink jet type has advantages of a low noise, a low running cost and a function of color printing. Such ink jet printers include a serial printer and a line printer. The serial printer prints an image by combining a movement in a main scanning direction in which ink droplets are discharged while a record head moves in the main scanning direction (a width direction of the recording medium) and a movement of the rewording medium in a sub scanning direction. The line printer is provided with a line head having a print width for the width of the recording medium, and prints while moving the line head and the recording medium relatively.
The line printer includes a continuous paper printer which uses a continuous paper as a recording medium, which is suitable for large amounts of printing. The continuous paper printer prints while conveying continuous paper wound in a roll at high speed (for example, 0.5 to 2 m/s).
On the other hand, there is an ink jet printer having a configuration of printing both sides of a continuous paper, from a standpoint of resource saving, by a tandem operation using two continuous paper printers, i.e. printing a first side of the continuous paper (for example, top side) by the first continuous paper printer, inverting the continuous paper, and printing a second side of the continuous paper (for example, back side) by the second continuous paper printer.
Recently, in the above-described ink jet printers, image quality becomes higher and higher, since a discharge timing of an ink droplet and a size of an ink droplet can be finely controlled. However, in the ink jet printer, ink droplets are discharged to form an image, and until the ink droplets are dried, impacted dots blur along a paper fiber. Accordingly, a phenomenon such as feathering or color bleed, in which a color border becomes blurred by mixing with an adjacent ink droplet with different color, easily occurs, and the quality of an image degrades.
As a method of inhibiting the degradation of the quality of the image, there is the art of applying treatment agent liquid such as a blurring inhibitor on the recording medium as a preprocessing, so as to inhibit the blurring of ink by aggregating a component of pigment in the ink droplet.
Such kind of treatment agent liquid application device as above includes a supply pan that stores the treatment agent liquid, an application roller that applies the treatment agent liquid on a record surface of the recording medium, a squeeze roller that draws up the treatment agent liquid in the supply pan, thins the treatment agent liquid and transfers it to the application roller, a pressure roller that conveys the recording medium while holding it with the application roller, and the like.
In the treatment agent liquid application device as described above, it is proposed that in order to remove a foreign matter such as paper dust attached on a surface of the squeeze roller, a swirling current with high flow velocity is generated in the supply pan, and a partition which is orthogonal to a rotational direction of the squeeze roller is provided.
Moreover, it is proposed that in order to prevent the treatment agent liquid in the supply pan from evaporating, the treatment agent liquid, the squeeze roller and the application roller are housed in the supply pan (housing).
For example, Japanese Published Patent Applications No. 2012-238374 and 2012-56261 disclose the treatment agent liquid application device described as above.
In the treatment agent liquid application device of the related art, when the treatment agent liquid is drawn up by rotating the squeeze roller a part of which is immersed in the treatment agent liquid in the supply pan, a position of fluid level varies greatly, and a liquid amount of the treatment agent liquid in the supply pan may not be detected correctly.
Accordingly, an uneven application or an application failure may occur due to an insufficient supply of the treatment agent liquid, and the function of the treatment agent liquid cannot be fulfilled. Moreover, contrary to the above, due to an excess in supply of the treatment agent liquid, the treatment agent liquid overflows from the supply pan into the application device and a liquid dispersion occurs. Accordingly, a problem that the inside of the application device is smeared or an electric part is damaged will occur.
The shortage of supply or the excess in supply of the treatment agent liquid, described as above, depends on a speed of application of the treatment agent liquid. Particularly, for the application device in which plural application speeds are set, it is necessary to be careful so that the shortage of supply or the excess in supply of the treatment agent liquid does not occur for each of the application speeds.
Moreover, the shortage of supply or the excess in supply also depends on a viscosity of the treatment agent liquid. It is necessary to respond to a change in the viscosity of the treatment agent liquid associated with water evaporation. Particularly, for the application device using plural kinds of treatment agent liquids, changes in viscosity characteristic of which are different from each other, the above-described problem becomes complicated.
Japanese Published Patent Applications No. 2012-218374 and 2012-56261 do not disclose suppressing the variation of the position of the fluid level which occurs when the treatment agent liquid is drawn up by the squeeze roller rotating, and resolving the problem due to the shortage of supply or the excess in supply of the treatment agent liquid.